Abstract

The correlation between the crystalline quality of low-temperature GaN (LT-GaN) films and current collapse in heterostructure field-effect transistors with a LT-GaN cap layer was investigated. LT-GaN cap layers were grown at various temperatures ranging from . No current collapse was observed for heterostructure field-effect transistors with LT-GaN cap layers grown at 500 and . The crystalline quality of the -thick LT-GaN filmsgrown at was then studied through x-ray diffraction and selected area electron diffraction measurements. The crystalline quality, considered by measuring the full width at half maximum through x-ray diffraction, deteriorated as the growth temperature decreased. The crystal structure of LT-GaN filmsgrown at 500 and was confirmed as polycrystalline. Thus, the results demonstrated that in heterostructure field-effect transistors, a polycrystallinestructure provides the most effective LT-GaN cap layer for suppressing current collapse.